On an electronic part, generally, chip parts including a semiconductor IC and so forth are enclosed in a shielding case, for assuring electromagnetic compatibility (EMC). Also, in order to avoid short circuit caused by contact of the shielding case and a power source of the chip parts in the shielding case, the shielding case is made sufficiently high to thereby secure a clearance between the shielding case and the chip parts.
Recently, it is becoming more difficult to secure the clearance between the shielding case and the chip parts enclosed therein, under the restriction imposed by requirement for reducing the thickness of a device in which the electronic part is to be implemented.
In particular, the shielding case is often encapsulated with a resin through an opening provided on a top face of the shielding case, to secure drop strength of a terminal portion of the chip parts in the shielding case. With such structure, in the case where bending force is applied from outside to the top face of the shielding case, stress is concentrated at the opening on the top face of the shielding to thereby warp the edge of the opening, which may bring the shielding case and the chip parts in the shielding case into contact and thus causing short circuit and resultant malfunctions such as erroneous action and abnormal heat generation.
Accordingly, in order to avoid short circuit caused by contact of the shielding case and the chip parts in the shielding case, the shielding case is made sufficiently high to thereby secure a clearance between the shielding case and the chip parts, which, prevent reducing the thickness of the device.
Regarding such problem, the following related arts can be found.
One is a high-frequency electronic part having increased strength while maintaining shielding performance of an outer case, which includes a substrate, surface-mounted parts, and the outer case; and the surface-mounted parts include a first terminal electrode and a second terminal power source provided for inputting/outputting a high-frequency signal or applying a source voltage; the surface-mounted parts have a surface opposing the outer case formed in a flat plane; the first terminal electrode includes a first folded portion formed on a surface opposing the outer case; the second terminal electrode includes a second folded portion formed on a surface opposing the outer case; and the outer case includes a first opening formed so as to expose the first folded portion, a second opening formed so as to expose the second folded portion, and an intermediate portion between the first opening and the second opening (for example, refer to the patent document 1).
An object of the foregoing patent document is to keep the outer case and the electrodes from contacting each other by forming the openings on the outer case, thereby reducing the distance between the outer case and the surface-mounted parts and thus reducing the height of the electronic part. However, since the openings are made small from the viewpoint of strength of the outer case, shielding effect against electromagnetic interference, and intrusion of a foreign substance, such openings are inappropriate for providing the resin therethrough, for securing the drop strength of the terminal portion of the chip parts as stated above.
Another one is a circuit substrate device that simplifies a bonding process of the shielding case and reducing the size thereof, in which electronic parts are mounted along a periphery of a substrate with the respective terminal electrodes of ground potential facing the periphery of the substrate, and the inner wall of the shielding case is brought into contact with the terminal electrodes of ground potential of the electronic parts and conductively bonded therewith (for example, refer to the patent document 2).
The object of the patent document 2 is to simplify the bonding process of the shielding case and reducing the size thereof, by bringing the inner wall of the shielding case into contact with the terminal electrodes of ground potential of the electronic parts and conductively bonding. However, such technique is not intended for minimizing the distance between the shielding case and the chip parts thereby reducing the thickness of the device, in the electronic part encapsulated with the resin for securing the drop strength of the terminal portion of the chip parts, as stated above.    [Patent document 1] JP-UM No. 3111672    [Patent document 2] JP-A No. 2000-106475